Surface Acoustic Wave (SAW) devices are frequently used as filters, signal processing components, and as the resonating components of oscillators for generating sinusoid signals. Use of these devices is typically limited to applications where a fixed or slightly tunable frequency response is suitable.
In contrast to a Bulk Acoustic Wave (BAW) device where the resonant frequency is generally determined almost exclusively by the physical properties and geometry of the piezoelectric material, the bandpass frequency and propagation delay properties of a particular SAW device are largely influenced by the mechanism by which signals are applied to and extracted from the piezoelectric substrate as well as the material properties. This mechanism is traditionally determined by a fixed metallization pattern known as the interdigitated transducer (IDT) which contains a single pair of connection terminals for the input signal and a similar pair of terminals for the output signal. A typical SAW device contains a sending and a receiving IDT.
Because of their elongated parallel structure, the interdigitated transducers (IDT) are also referred to as transducer fingers or just “fingers”.